A touch sensing display device is a display device that receives a user's input commands via a touch panel having a function of sensing touches. Generally, an adhesive material is utilized to assemble the touch panel and display device as the touch sensing display device. Nowadays, a technique for directly disposing sensors on the display device to detect a touch event has been developed. The display device utilizing this technique is called an embedded touch sensing display device.
Please refer to FIG. 1, which is a diagram showing a cross-sectional view of a structure of a conventional touch sensing display device. The conventional touch sensing display device is a liquid crystal display (LCD) device disposed with touch sensors. The LCD panel includes a thin-film transistor (TFT) array substrate 10, a color filter (CF) substrate 20, and a liquid crystal layer (not shown) disposed therebetween. A dielectric layer 12 and a passivation layer 14 are disposed on the TFT array substrate 10. Indium tin oxide (ITO) layers 15, 25 are respectively disposed on the TFT array substrate 10 and the CF substrate 20 for serving as a pixel electrode and a common electrode to orient liquid crystal molecules.
A spacer 35 is disposed on the CF substrate 20. The spacer 35 is covered by the ITO layer 25, which is used as the common electrode. When a user touches the panel at a position where the spacer 35 is located, the spacer 35 moves downward so that the ITO layer 25 under the spacer 35 touches the ITO layer 15 on the TFT array substrate 10. At this moment, the ITO layers 15, 25 contact to be shorted with each other. The ITO layer 15 is a resistive film. When the ITO layers 15, 25 at different positions of the panel contact to be shorted with each other, different voltages will be detected. Therefore, a two-dimensional coordinate of a touch point can be determined according to the detected voltage.
Please refer to FIG. 2a, which is a diagram showing a cross-sectional view of a structure of another conventional touch sensing display device. The same components are indicated by the same reference numbers as in FIG. 1. As shown in FIG. 2a, two separate metal pads 17 are disposed on a TFT array substrate 10. The two metal pads 17 are disposed in correspondence to a spacer 35 on a CF substrate 20 as shown. When a user touches the panel at a position where the spacer 35 is located, the ITO layer 25 under the spacer 35 contacts both the two metal pads 17, and thus electrically connecting the two metal pads 17. The voltage at the ITO layer 25 serving as a common electrode is thereby transmitted to the metal pads 17.
Please refer to FIG. 2b, showing a layout of the conventional touch sensing display device in FIG. 2a. As shown in FIG. 2b, an X independent sensing line (XL) parallel to a source line (SL) and a Y independent sensing line (YL) parallel to a gate line (GL) are disposed on the display panel. The gate line (GL) transmits a scan signal to control a thin-film transistor, and the source line (SL) transmits pixel data. The X independent sensing line (XL) and Y independent sensing line (YL) are respectively connected to the two metal pads 17. When the ITO layer 25 contacts the two metal pads 17, the voltage of the ITO layer 25 is transmitted to the X independent sensing line (XL) and Y independent sensing line (YL). The two-dimensional coordinate of a touch point can be determined according to a voltage variation of the X sensing line (XL) and a voltage variation of the Y sensing line (YL) on the display panel.
In each of the two conventional touch sensing display devices mentioned above, the voltage of the common electrode will be affected, and this leads to an unstable problem of displaying images. In addition, the lateral or peripheral side of the spacer 35 is covered by the ITO layer 25. This will cause a fringing electric field phenomenon so that the image displaying quality is degraded. Moreover, parasitic capacitances will be generated among the X sensing line (XL), Y sensing line (YL), gate line (GL), and source line (SL). The image displaying may be abnormal when the parasitic capacitances are considerable.